A GUIDE AND KEY TO AQUATIC PLANTS 115 



3. P. lapathifolium L. — Most common in alluvial marshes and 

 swamps along rivers, range covering all of our territory. It has on 

 occasion been found in association with Anopheles quadrimacvlatus. 



4. P. densiflorum Meisn. — Range includes all of our Coastal Plain. 

 Said to be found in swamps, ponds, and along lake-borders. 



5. P. longisiylum Small — Should be expected only in the extreme 

 western part of our territory. 



6. P. pensylvanicum L. Smartweed — Distributed over all of om* 

 territory, both in aquatic and non-aquatic situations. Most com- 

 mon, perhaps, in alluvial marshes and Anopheles quadrimaculatus has 

 been found associated with it occasionally. 



7. P. hydropiper L. Water-pepper — Ranges over all of our terri- 

 tory, often not truly aquatic. When found in water, generally 

 prefers neutral or alkaline conditions. 



8. P. pundatum Ell. — Shows a wide acidity tolerance and, like 

 many of this genus, is equally at home in the water and on land. 

 Range covers all of our territory, and breeding of Anopheles quadri- 

 maadatus has occasionally been found associated with it. 



9. P. persicaria L. — Most often found on land, occasionally truly 

 aquatic. Range includes all of our territory. 



10. P. hirsuium Walt. — Coastal Plain, Florida and Georgia. 

 Collected from acid limesink ponds and other very acid situations. 



11. P. setaceum Baldw.— This Water-pepper is found over all of 

 our Coastal Plain. The writers have encountered it most frequently 

 in acid situations. 



12. P. hydropiperoides Michx. — Various provinces over all of our 

 territory. Anopheles quadrimaculatus found associated with it at 

 Reelfoot Lake, Tennessee. 



13. P. opelousanum Ridd. — Various provinces over all of our terri- 

 tory. The writers have not often noted it owing to its similarity to 

 the preceding species. 



AMARANTHACEAE Amaranth family 

 1. Acnida L, 



A. cuspidata Bertero — Huge herb, the largest in our flora, found in 

 marshes and swamps, Coastal Plain, Florida to Louisiana. The stem 

 at the base of the plant sometimes reaches over a foot in diameter. 



2. Alternanthera Forsk. 



A. philoieroides (Mart.) Griseb. Alligator-grass — Pestiferous spe- 

 cies, naturalized from South America and often found in alluvial areas. 

 Found in a variety of aquatic areas. Coastal Plain, Florida to North 

 Carolina and westward. In the Tennessee Valley it has become 

 introduced and verv often harbors larvae oi Anopheles quadrimacidatus. 

 This species is listed by SmaU under the genus Achyranthes. 



